Wellington - New Zealand is reluctant to send more troops to Afghanistan because it believes the situation there is becoming more unstable, Prime Minister John Key said Monday.

"The determining factor is whether we can see a plan, whether the plan in our opinion is likely to work and whether it fits in with our long-term exit strategy," he said at his weekly news conference.

The United States has asked New Zealand to commit more troops to Afghanistan on top of the 130 army engineers it has working in Bamyan province as a provincial reconstruction team (PRT).

News reports have said that Washington would like a unit of New Zealand's crack Special Air Services forces, who were last deployed in Afghanistan in 2006, to return as part of President Barack Obama's plan to increase foreign troop levels in Afghanistan to better combat Taliban and al-Qaeda fighters.

But Key said, "The risk assessments that I'm getting from Afghanistan is that our troops in the PRT in Bamyan province are becoming more at risk - in other words, the situation in Afghanistan is becoming more unstable.

"It would be my long-term desire to exit our commitment in Afghanistan," he said.

Key said the government was reviewing the military situation in Afghanistan before it made a final decision on sending more troops. (dpa)